Method for the manufacturing of elements of non-ferrous metal alloys, advantageously aluminium alloys

ABSTRACT

A method is disclosed for the manufacturing of elements of non-ferrous metal alloys, advantageously aluminium alloys, used for the manufacturing of shaped elements, in particular rods, in thermal treatment of metals. The charge will be subjected to plastic working of at least 60% deformation, advantageously by pressing with the degree of processing exceeding the value of 2, at a temperature below the range of occurrence of a solid solution, after which the obtained element undergoes the supersaturation process by heating it up to the temperature of occurrence of a solid solution and keeping it at this temperature for a period of 2-25 minutes, advantageously 5 minutes, and then rapidly cooled, advantageously using water, to the ambient temperature, after which it is subjected to the ageing process.

CROSS-REFERENCE TO RELATED U.S. APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT Not applicable. REFERENCETO AN APPENDIX SUBMITTED ON COMPACT DISC Not applicable. BACKGROUND OFTHE INVENTION

1. Field of the Invention

The subject of the invention is a method for the manufacturing ofelements of non-ferrous metal alloys, advantageously aluminium alloys,used for the manufacturing of shaped elements, in particular rods, inthermal treatment of metals.

2. Description of Related Art Including Information Disclosed Under 37CFR 1.97 and 37 CFR 1.98.

In order to achieve high strength properties, alloys with differentsolubility when solid, in particular finished products or semi-finishedproducts undergo thermal treatment, which consists of a supersaturationoperation and ageing operation, or thermal and thermo-mechanicaltreatment, composed of, in the following order: supersaturationoperation, plastic deformation and ageing operation.

The supersaturation operation consists of heating the alloy totemperature from the range of a solid solution, annealing it for a timenecessary to dissolve the secondary phase particles and rapid cooling,as a result of which the alloy in the ambient temperature remains in asingle-phase structure, which will be thermodynamically unstable andwill transform during the ageing operation. This operation consists ofthe heating of the supersaturated alloy to the temperature below thesolubility limit and annealed for the time required for precipitationfrom the supersaturated solid solution of phases with a high degree ofdispersion.

Usually, the thermal treatment is conducted on elements with initiallyor finally shaped geometry, as a result of casting, machining or plasticworking If plastic working is conducted in an appropriately hightemperature, which guarantees the alloy will achieve the structure of asolid solution, rapid cooling of the deformed element will result in itssupersaturation. In particular, in case of high-temperature pressing ofthe alloy, the supersaturation may be performed directly at the pressdelay route, through intensive cooling of the compact, usually withwater. Single-phase structure of the alloy, which results from thesupersaturation operation, increases its plastic properties and enablesintense plastic working of the alloy, up to achieving a product withfinal geometry, and subsequently the used aging process, as well as theassumed mechanical properties.

Since the annealing of the alloy in an appropriately high temperature,which is an element of the supersaturation, is intended to dissolve thephases and obtain a solid solution, the time of annealing necessary forthe full occurrence of the heat activated process of diffusion of alloycomponents amounts usually from 1 to a few hours. The conditions ofalloy annealing are not differentiated depending on whether it was orwas not subjected to initial plastic working

In accordance with the method of aluminium alloy element manufacturing,a charge with dimensions of 40×40 mm, of a 7075 aluminium alloy, waspressed on a hydraulic press with a speed of 0.5 mm/s within atemperature of 450° C. to which both the charge and the working toolswere heated, after which the charge was annealed within this temperaturefor 2 hours. The obtained rod with a diameter of 12 mm was immediatelycooled with water. Then, the rod was aged by annealing at a temperatureof 150° C. for a time of 3 hours. As a result, the rod obtained ahardness of 160 HV.

In accordance with another used so far method of manufacturing ofaluminium alloy elements, in particular of 7075 aluminium alloy, acharge with dimensions of 40×40 mm was pressed on a hydraulic pressequipped with a mechanical system resulting in oscillating rotation ofthe die along its axis with an angle of ±8° with a frequency of 5 Hz.The process of pressing was conducted at a speed of 0.5 mm/s at atemperature of 20° C., without initial heating of the charge and thetools, obtaining a rod with a diameter of 12 mm, which was immediatelycooled in water. Then, the rod was aged by annealing at a temperature of150° C. for a time of 3 hours. As a result, the rod obtained a hardnessof 137 HV.

BRIEF SUMMARY OF THE INVENTION

The essence of the invention, which is a method of manufacturingnon-ferrous metal alloy elements, with the use of plastic working andthermal treatment, advantageously aluminium alloys, consists of themetallic charge being subjected to a plastic deformation of at least60%, advantageously by pressing with the extrusion ratio exceeding thevalue of 2, at a temperature below the range of occurrence of a solidsolution, after which the obtained element undergoes the supersaturationprocess by heating it up to the temperature of occurrence of a solidsolution and keeping it at this temperature for a period of 2-25minutes, advantageously 5 minutes, and then rapidly cooled,advantageously using water, to the ambient temperature, after which itis subjected to the ageing process.

It is advantageous when plastic working is conducted by pressing withoscillating rotations of the die along its axis with an angle in therange of ±(4-25)° and a frequency in the range of 1-15 Hz.

It is also advantageous when plastic working is conducted by rolling,with at least one of the working rollers moving along its axis or anadditional working tool, restricting the roll gap, whereas the movementrange may not be higher than 10 mm, and the frequency may not be lowerthan 2 Hz.

DETAILED DESCRIPTION OF THE INVENTION

The use of the solution presented in the invention obtains a technicaland utility effect, which is the shortening of the time needed to annealalloys during a supersaturation operation, while simultaneouslyincreasing its strength properties. The higher the deformation obtainedbefore the thermal or thermal and mechanical treatment is, the shorterthe annealing time, whereas the minimum deformation value should be 60%.The most advantageous effects are obtained when the initial deformationof the alloy is conducted in condition of a variable deformation path,implemented by the change of the load scheme, which is obtained in thepressing process through the additional use of oscillating die rotationsalong its axis by an angle in the range of ±(4-25)° and a frequency inthe range of 1-15 Hz.

Shortening the annealing time in the supersaturation operation with themethod presented in the invention is possible due to the generationduring the initial deformation of the alloy an above-equilibriumconcentration of point defects, advantageously in the conditions ofchange of the path of deformation. On one hand, these defects along withthe atoms of alloying elements in the temperature below the temperatureof occurrence of a solid solution create relatively mechanically andthermally stable nano-sized clusters, which hinder the diffusion, andthus the effectiveness of the aging operation. On the other hand, if theaging operation will be preceded by a classic supersaturation operation,including short-term annealing at the temperature from the range of asolid solution presence, the clusters dissolve and point defects arereleased, significantly accelerating the new phase precipitation. Thus,the higher the annealing temperature is in the super-saturationoperation, the shorter the super-saturation time.

The method presented in the invention results in the increase of thestrength properties of the products and the efficiency of technologicalprocesses including the thermal and thermo-mechanical treatment, isenergy-saving and environmentally friendly.

EXAMPLE

Charge of the 7075 aluminium alloy with dimensions of 40×40 mm waspressed on a hydraulic press equipped with a mechanical system resultingin oscillating rotation of the die along its axis with an angle of ±8°with a frequency of 5 Hz. The process of pressing was conducted at aspeed of 0.5 mm/s at a temperature of 20° C., without the initialheating of the charge and the tools, obtaining a rod with a diameter of12 mm, which after air cooling was subjected to rod super-saturationoperation, which includes 2 min long heating up to a temperature of 470°C., holding this temperature for 5 min, after which rapid cooling withwater was conducted. Then, the rod was aged by annealing at atemperature of 150° C. for a time of 3 hours. As a result, the rodobtained a hardness of 192 HV.

1. A method of manufacturing non-ferrous metal alloy elements, with theuse of plastic working and thermal treatment, advantageously aluminiumalloys, wherein the charge will be subjected to plastic working of atleast 60% deformation, advantageously by pressing with the extrusionratio exceeding the value of 2, at a temperature below the range ofoccurrence of a solid solution, after which the obtained elementundergoes the supersaturation process by heating it up to thetemperature of occurrence of a solid solution and keeping it at thistemperature for a period of 2-25 minutes, advantageously 5 minutes, andthen rapidly cooled, advantageously using water, to the ambienttemperature, after which it is subjected to the ageing process.
 2. Amethod in accordance with claim 1, wherein plastic working is conductedby pressing with oscillating rotations of the die along its axis with anangle in the range of ±(4-25)° and a frequency in the range of 1-15 Hz.3. A method in accordance with claim 1, wherein plastic working isconducted by rolling, with an over the axis movement of at least one ofthe working rollers or an additional working tool, restricting the rollgap, whereas the movement range may not be higher than 10 mm, and thefrequency may not be lower than 2 Hz.